This invention relates to safety pressure relief apparatus and has particular reference to such apparatus incorporating reverse buckling discs.
A reverse buckling pressure relief disc as referred to in this specification has a central portion which is convex on one side and concave on the other and which is held between two annular members around an edge region of the disc. In use, the pressure relief apparatus incorporating the disc and annular members is located upon a vessel with the convex side of the disc facing towards the interior of the vessel so as to be in direct contact with the fluid contained within the vessel. When the fluid pressure within the vessel reaches a predetermined limit, the disc reverses itself.
In known constructions of safety pressure relief apparatus incorporating reverse buckling pressure relief discs, cutting devices are provided on the outer side of the discs whereby when the discs are reversed, they become impaled on the cutting devices and are thus punctured so as to allow the fluid under pressure to escape from the vessel. These discs are normally referred to as reverse buckling pressure relief discs which are intended to rupture to permit fluid under pressure to escape. In an alternative form, there are devices in which the reverse buckling pressure relief disc is not intended to rupture by contacting a cutting device, but is intended to become reversed and then forced by fluid pressure to move from the position in which it is located so as to enable the fluid to escape from the vessel. In one construction, a reverse pressure relief disc of the latter construction is located in a pressure relief passage with the edge of the disc disposed against an annular shoulder which faces inwardly towards the interior of the pressure vessel. The edge of the disc is sealed against this shoulder by being soldered to it. The soldering operation is inconvenient to perform and it would be advantageous to avoid it.
In a further known construction, the reverse buckling disc is clamped between two planar parallel gripping surfaces and on reversing pulls free from the planar surfaces and permits the disc to be released.